This invention relates to water distillation apparatus and in particular to an add-on control unit for a modular distillation apparatus.
A water distillation apparatus including a steam generator and a condenser for condensing steam into distilled water is useful in improving the quality of water for domestic consumption. One such distillation apparatus is provided in modular form with a distillation unit and several add-on accessories that enhance the utility of the distillation unit. One add-on accessory is a large capacity holding tank to receive distilled water produced by the distillation unit. Another accessory is a level monitoring unit that may be mounted to the top of the holding tank in order to deenergize the still when the holding tank is full.
One prior art level monitoring unit 100 is shown in FIG. 3. This unit includes a base 101 that may be connected to a top 22 of the holding tank. A float assembly 102 extends through an opening 27 in the holding tank top and rises when the level increases beyond the location of float 102 illustrated in FIG. 3. Float 102 is connected to a power switch 103 and switches the contacts of switch 103 from a normally closed to an open state as float 102 rises. The contacts of power switch 103 are electrically connected in series between a power cable 104 and a receptacle 105. In such a prior art modular distillation unit, the still receives its power from receptacle 105. As long as the level of water in the holding tank is below the position of float 102, as shown in FIG. 3, the normally closed contacts of power switch 103 provide power from power cable 104 to the still to produce distilled water. As the holding tank becomes full, float 102 rises and eventually causes the normally closed contacts of switch 103 to open to remove power to the still.
The difficulty with such a prior art modular unit is that the level of distilled water in the holding tank rises very slowly. Even though power switch 103 is a snap-actuated switch, the slow rate of actuation of the switch by the float and the large current flowing through the switch to operate the still may cause extensive arcing and potential switch failure. In addition, the only function performed by the holding tank level monitoring unit is to disable the still when the holding tank is full. If the distillation unit is to be automatically controlled, i.e., not require manual filling, the basic distillation unit must come equipped with such control. This requires separate configurations of the distillation unit for manual versus automatic operation.